Thwarting Control Plane Attacks with Displaced and Dilated Address Spaces

To maintain the control-flow integrity of today’s machines, code pointers must be protected. Exploits forge and manipulate code pointers to execute arbitrary, malicious code on a host machine. A corrupted code pointer can effectively redirect program execution to attacker-injected code or existing code gadgets, giving attackers the necessary foothold to circumvent system protections. To combat this class of exploits, we employ a Displaced and Dilated Address Space (DDAS), which uses a novel address space inflation mechanism to obfuscate code pointers, code locations, and the relative distance between code objects. By leveraging runtime re-randomization and custom hardware, we are able to achieve a high-entropy control-flow defense with performance overheads well below 5% and similarly low power and silicon area overheads. With DDAS in force, attackers come up against 63 bits of entropy when forging absolute addresses and 18 to 55 bits of entropy for relative addresses, depending on the distance to the desired code gadget. Moreover, an incorrectly forged code address will result in a security exception with a probability greater than 99.996%. Using hardware-based address obfuscation, we provide significantly higher entropy at lower performance overheads than previous software techniques, and our re-randomization mechanism offers additional protections against possible pointer disclosures.